export function fib(n: number): number {
    if (n < 2) return n;
    let one = 0;
    let two = 1;
    // ret = one + two
    let ret = 0;
    let i = 2;
    while (i <= n) {
        ret = one + two;
        one = two;
        two = ret;
        i++;
    }

    return ret;
};